Pentagonal Bipyramidal Molecular Geometry

Pentagonal bipyramidal molecular geometry
Examples	IF 7, ZrF3− 7
Point group	D5h
Coordination number	7
Bond angle(s)	90°, 72°
μ (Polarity)	0

In chemistry, a pentagonal bipyramid is a molecular geometry with one atom at the centre with seven ligands at the corners of a pentagonal bipyramid. A perfect pentagonal bipyramid belongs to the molecular point group D_5h.

The pentagonal bipyramid is a case where bond angles surrounding an atom are not identical (see also trigonal bipyramidal molecular geometry).^[1] This is one of the three common shapes for heptacoordinate transition metal complexes, along with the capped octahedron and the capped trigonal prism.^[2][3] Pentagonal bipyramids are claimed to be promising coordination geometries for lanthanide-based single-molecule magnets, since they present no extradiagonal crystal field terms, therefore minimising spin mixing, and all of their diagonal terms are in first approximation protected from low-energy vibrations, minimising vibronic coupling.^[4]

• Iodine heptafluoride (IF₇) with 7 bonding groups
• Rhenium heptafluoride (ReF₇)
• Peroxo chromium (IV) complexes, such as [Cr(O₂)₂(NH₃)₃], where the peroxo groups occupy four of the planar positions.
• ZrF3−7 and HfF3−7^[5][6]

• [1] – Images of IF₇
• 3D Chem – Chemistry, Structures, and 3D Molecules
• IUMSC – Indiana University Molecular Structure Center

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